That’s not possible — not anymore. Last week, the magazine, known for a chatty, pop-culture approach to serious science, announced that it was shutting off online comments. “Comments,” an editor wrote in an online post, “can be bad for science.”

The magazine said that vicious, insulting or ignorant comments can pollute otherwise intelligent online discussions and undermine public understanding and appreciation of science itself. “Trolls and spambots,” it said, sometimes hijacked the conversation, particularly on divisive issues like climate change and evolution.

For example: “BUNK,” one commenter said of an article posted in August about scientists finding fossil evidence that mammals weren’t the first creatures with fur. “What this actually shows is that evolution is still nonsense and doesn’t work.”

Even on sites where comments are actively screened — like Nytimes.com, where moderators either post or reject submissions — people who think evolution is bunk are generally permitted to voice their view, often to be shouted down by others; for some readers, following such comment threads is part of the fun. But Popular Science and other publications do not have the resources to moderate all comments, so personal attacks and other bits of ugliness can slip in.

Still, the move to silence what many online readers consider a digital town square has ignited a burst of reaction from bloggers and commentators on science and the media, as well as editors at other science magazines. Many sympathized with the feeling that a Wild West of uncouth, illogical commenters can infect the tenor of discussion.

“Unless a comment stream is actively moderated, it inevitably is ruined by bullies, hotheads and trolls,” James Fallows wrote, explaining why he does not allow comments on his columns on The Atlantic’s Web site.

But others called Popular Science’s move too extreme, disagreeing that public support for science could be imperiled by unbridled comments. Some people said that comments, when kept under control, could benefit science, fostering debate and displaying what Will Oremus, on Slate, called the “spirit of free inquiry that has always driven scientific discovery.”

“I have to say I don’t think comments are bad for science,” Fred Guterl, executive editor of Scientific American, said in an interview. “To a point I think it’s good when people talk about things and try their ideas out,” he said. “Social media can cause things to go off the rails, but I don’t think comments are worse than Twitter.”

Popular Science’s online content director, Suzanne LaBarre, wrote that that study, and another involving some of the same researchers, imply a discomfiting spiral: “commenters shape public opinion; public opinion shapes public policy; public policy shapes how and whether and what research gets funded.”

Ms. LaBarre said in an interview that Popular Science could not afford comment moderators. Its writers monitor and delete comments that are “racist or sexist or homophobic,” she said, but usually stop as they move on to their next story.

Two other science journals said they did not hire moderators, yet had inexpensive ways to keep comments on a polite track.

At Nature, public comments on news articles and features are removed if editors or readers flag them as abusive or as spam, Noah Gray, a senior editor, said.

“There’s no doubt that uncivil discourse is bad for science,” Dr. Gray said by e-mail.

But, he said, comments can be very valuable, sometimes pointing out errors or alternative interpretations of the facts and theories presented in the article.

“The comments section can often express the openness of scientific debate,” Dr. Gray said, adding, “Removing this channel for feedback rather than exploring an alternative means to improve it simply ignores the problem.”

Scientific American uses what Mr. Guterl called a “sort of soft approach.”

Writers of articles are asked to participate in the comments and “add their own voice to them,” he said, so “you can set a tone without having to be dictatorial.”

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Scientific American’s blogs editor, Bora Zivkovic, said communities of commenters sometimes aided the cause of science, solving math mysteries or helping spur retractions of poor-quality scientific papers. But if sites don’t have “the time and energy to really work on comments, then it’s better not to have them,” he said.

When he started his job a few years ago, “it was a real cesspool in the commenting threads,” Mr. Zivkovic said, with “creationist denialists of all sorts dominating our comments, and they were often quite nasty.”

Slowly, he began deleting offensive comments, giving warnings, and posting his own in respectful language. It was like “getting into a garden that’s completely covered with weeds so you have to use a weed whacker,” he said.

Ms. LaBarre of Popular Science said that comments trafficking in conspiracy theories seemed to be “undermining scientifically sound” stories. On an article about global warming, for example, one commenter wrote: “Yeah, right....Gullible Warming. What a crock!”

So when the Wisconsin study appeared, “it confirmed a lot of the things we were already thinking,” Ms. LaBarre said.

The study asked 1,183 people to read an article about a fictitious type of nanotechnology, a scientific subject chosen because most people know little about it and have no strong ideological views, said Dietram Scheufele, one of the researchers.

The study found that people who read uncivil comments ended up more polarized in their views of the technology than those who read civil comments. Those who started off with a negative view of the technology thought it was even riskier when they read a comment like “This is a risk, you idiot,” Dr. Scheufele said.

And people who started off with a positive view thought it was even safer when they read a comment like “You’re stupid — this is a benefit.”

“There’s no way that a completely unmoderated discussion is not going to be detrimental to the facts,” Dr. Scheufele said. “But I’m torn. I do know that we need to learn how to have these debates.”

Some science journalists said they thought the results of the Wisconsin study were too subtle or unsurprising to justify banning comments.

Dr. Gray questioned whether the study accurately “mimics the natural engagement of the reader with the science blog post and comments.”

Ms. LaBarre said Popular Science would be starting a network of blogs, and might try different commenting approaches on those.

One reader, Steve Thorson, pleaded in an e-mail, “Please don’t turn off comments,” adding: “Popsci commenters have helped me understand articles that were over my head. I need them.”

Another e-mail, from Nick Anglewicz, archly included both points of view: “I think you’ve made the right decision, thanks for the explanation,” he wrote. “Now if only I could state my opinion on your post publicly on the Web site.”

A version of this article appears in print on October 1, 2013, on Page D1 of the New York edition with the headline: Comment Ban Sets Off Debate. Order Reprints|Today's Paper|Subscribe